3857. Minimum Cost to Split into Ones

You are given an integer n.

In one operation, you may split an integer x into two positive integers a and b such that a + b = x.

The cost of this operation is a * b.

Return an integer denoting the minimum total cost required to split the integer n into n ones.

class Solution {
public:
    int minCost(int n) {
        return 1ll * n * (n - 1) / 2;
    }
};